Far infrared radiators convert thermal energy into far infrared rays having a wavelength of 2-30 μm as a result of heating. These far infrared rays are radiated to the outside, enabling them to be used in a wide range of applications including heaters, dryers, curing devices and heat sinks.
One type of such a far infrared radiator is disclosed in, for example, Japanese Unexamined Patent Application, First Publication No. 63-145797. In this far infrared radiator, an anodic oxidization film having a thickness of 10 μm or less is formed on aluminum or aluminum alloy, and an oxide of a metal such as iron (Fe), chromium (Cr), nickel (Ni) or cobalt (Co) is precipitated on the surface and in the micropores of this anodic oxidation film by electrolytic treatment.
However, in this far infrared radiator, the spectral emissivity in the wavelength region of 7 μm or less required for heating and drying is only 40-50%, thus making its performance as a far infrared radiator inadequate.
In addition, although an example of another far infrared radiator consists of dyeing an aluminum anodic oxidation film with black dye, this far infrared radiator has the shortcoming of inferior heat resistance of 200° C. or less.
Moreover, that comprising anodic oxidation treatment of an aluminum alloy having an alloy component such as manganese (Mn) or silicon (Si) to form a black anodic oxidation film is described as a far infrared radiator in Japanese Examined Patent Application, Second Publication 7-116639 and U.S. Pat. No. 5,336,341.
In this example of the prior art, however, since the aluminum alloy has a special composition, it is subject to restrictions on its shape, thereby resulting in the disadvantage of being unable to obtain a far infrared radiator of any desired shape.
Thus, the object of the present invention is to provide a far infrared radiator that is free of any of the shortcomings of the far infrared radiators of the prior art, has high emissivity, ample heat resistance and can be formed into any desired shape.
In addition, another object of the present invention is to provide a production method of a far infrared radiator that has high emissivity, ample heat resistance and can be formed into any desired shape.